1) Field of the Invention
The present invention relates generally to agricultural implements such as self-propelled sprayers, and more specifically to such a vehicle which is towable for transport between field locations.
2) Related Art
Self-propelled sprayers of the type exemplified by the commercially available John Deere Model 6000 Hi-Cycle often include a tow bar arrangement so that the sprayer may be connected to a chemical supply vehicle or pickup truck for transport from location to location. Sprayers usually include a hydraulic steering mechanism such as a steering motor or a steering cylinder. Such a mechanism can adversely affect sprayer trailing in the towed configuration if steering fluid pressure is not relieved. Lateral movement of the tow bar during connection of the sprayer to the towing vehicle is also greatly hampered by fluid pressure in the steering lines.
Some sprayers utilize a bypass valve having a towing position which allows flow of fluid from one side to the other of the steering motor or cylinder during towing and tow bar connection. However, it is possible with such a system to inadvertently leave the valve in the towing position after towing and not realize that steering is disabled until after the engine is started and the drive is engaged. Also, on sprayers with steering cylinders, there are unequal volumes of oil moving on opposite sides of the ram because of the smaller effective area on the rod end side, and the bypass may not adequately relieve steering cylinder pressure because of the differential in fluid flow.